Another question: does either of those (Boox M92, Pocketbook Pro 912) allow to locally store websites, so that they are accessible offline, while conserving their page hierarchy?

Example: something similar to http://www.vatican.va/archive/ENG1104/_INDEX.HTM where there is an index page with one-depth links to other pages (in this specific case the information is available in other ways, but there are other similar sites he would like to have a copy of).